1. Field of the Invention
The present invention relates to an inkjet printing apparatus and a printing method therefor, and particularly relates to controlling the color of an ink dot to be printed with a plurality of types of inks in an overlapping manner.
2. Description of the Related Art
It is known that in an inkjet printing method, the color (color appearance) of a dot on a print medium which is printed with a plurality of color inks in an overlapping manner varies depending on the order in which these inks are ejected and an ejection time difference. Japanese Patent No. 4343481 discloses that nozzles for ejecting a plurality of color inks are placed at different positions in a conveyance direction of a print medium to have the same order in which the plurality of inks are ejected, and to keep constant an ejection time difference between the plurality of inks in any scan area. This can suppress a color difference.
However, the technique for reducing a color difference as disclosed in Japanese Patent No. 4343481 is basically to have the same order in which inks of different colors are overlapped (ejected). Accordingly, it is necessary to provide print heads having a specific nozzle arrangement and specialize a printing operation including a scan with the print heads and conveyance of a print medium, and it is difficult to carry out the technique disclosed in Japanese Patent No. 4343481 by using print heads and a printing operation which are generally and widely used. On the other hand, in a case where the colors of an image to be printed can be changed by not only maintaining the color appearance, but also controlling the color appearance to change the color, the degree of freedom of design of the image to be printed can be increased.